Amplitude modulator



Jan. 13, 1942. H. J. R. voN BAEYER ETAL 2,269,613

AMPLITUDE .MODULATOR Filed March 1. 1939 -OUTER L/NE ExTENs/ON MODULATED WA VE OUTPUT' MoDULATr/VG PoTENT/ALS INVENTORS NAA/6 JACOB RITTER VHN BAEYER, HANS 0770 RDOSEA/STEIN,

HERBERT MUT ATTORN EY Patented Jan. 13, 1942 UNITED `s'rfii'r ES PATENT, l-ofrluCP1 J AMPLITUDE Mourir-.Aron

Hans Jacob Bitter von Buyer, `Hans Otto Roosenstein, and Herbert Muth, Berlin, Germany, assignors to Telefunken Gesellschaft fur DrahtloseTelegraphie'm. b. H., Berlin, Germany, a=

. corporation of Germany- Applioation Maron 1', 1939, soi-iai No.5259g13e InfGermany February 11, 1938 4 claims.L icl. 17a-4115i rPrnodulation, of the anode current is absorbed by the space-charge grid; The stream of electrons It is known in the art that in the modulation of ultra-short waves 'in magnetron or oscillatingelectron circuit organizations, the desired amplitude modulation is invariably accompanied byv such' stray modiv issuing from'the cathode (here represented by .the waye generatorsystem),the'refore, will not be impaired'by the modulation process.

" A Now, the invention shall be explained more modulation in an oscillator tube is made possible by completely separating, wave generation means from the modulation process so that there is` no risk or chance of the in electrical regard, the

latter reacting upon the means for generating the waves. According to the invention, electron coupling relationship is established between they wave generation system consisting of a magnetron or an oscillating-electron system and a dis-1 n tinct `tube system in which the electron current issuing from thegenerator system is modulated and which puts out the useful or lsignal energy.

.It has been suggested in the prior art to couple the output circuit, say, of an antenna by way'of an electron coupling means withthe oscillation generator system. However, the sole purpose of this scheme has been to generate relatively large power with ultra-short waves. In fact, the

scheme was unsuited for modulation work.

' A control or modulation action may be broughtupon the electron current either by magnetic-or by electrical ways and means. 'Ihe only thing Ithat is essential is that .there should be no chance for vthe modulator actions reacting as far back as the generator system. The basic idea of the theV cathode gives lolf f a of tube in which type which ilows through a systemrwhich emits an electron pencil or beamk modulated at ultra-high frequency. It y which is the above-mentioned space-charge' grid. It is so l 'fully by 'referencexto the drawing, in'which:

Fig. 1 showsanfembodiment ofjthe invention employing a retarding-eld oscillator Fig. 2 illustrates the inventionfas'applied to a4 magnetron type of generaton'an'd j Fig.` 3 represents a further modification of the invention employing secondary electron emission. Figure 1v shows a tube comprisingl a cathode i, a positively biased accelerator lectrode l.` and a retarder electrode 3. It noted that this system operates as' a retardingficld' generator, the frequency of which is Igoverned by the transit time of the velectrons from the cathode to the retarder electrode` `as well as Aby the -tuning of the externall circuit l. Outsidey this retardingfield or oscillating-,electron system is disposed the positively biased grid l.' This grid corresponds to designed that optimum coupling conditions are obtained.V *This grid separates the ultra-highfrequency system comprising electrodes` i, 2, l

from the modulator systemA consisting ofthe control electrode 5 and' the collector or output electrode 6. Through the retarder'electrode 3 `flies a fraction of the electronsv oscillating bertween the electrodes i and 3. This -fraction of invention. is comparable with the principle underlying a space-charge gridl 4'0,

the present instance, the H will -be remembered that the space-charge grid (in the present instancevthe modulator means) from the cathode space (here represented bythe wave generator). Hence, capacitive reactions are` thus recluded. v

2. IlThe excess of current resulting from the electrons reaches the space between the grid I and-the anode i, and it -is here modulated by means of the control grid- 5.; Reaction by the modulation process upon the generation of waves is therefore completely precluded. vThe useful or signal energy, as shown, is put out at the anode 6 and fed, for instance, tothe aerial by way of a co-axial'type' of feeder or lead. In this connection it will be found expedient to close also the outer sheath or envelope of the line as illus'- trated to result in a radio-frequency circuit including 4, lest the shielding might beincomplete. In Figure 1 the ofter sheath i0 is extended as shown 'at i2 to overlap a conductivemember il associated withelectrode I. circuit so comthe positive grid l.

Another exemplifiedembodiment of the invention comprising a magnetron type of generator is shown in Figure 2 where i is. the cathode of the generator, 2' andv I" the two anode segments, and 1 the oscillation circuit between these segments. The two segments have openings 3', I". Through the latter a part of the ultra highfreqencye1ectroys reaches e outside andby way, for instance, ofthe posi ve annular grids l' and 4" into the modulator space. The modulation grid mounted at both ends. of the magnetronsystem are designed by l and S" and the two anodes are designated by. i' and 6".

As can be readily understood, the entire organization operates ix\ push-pull, with the grids 5', I" being modulated in phase. In order to transmit several signals the two grids 5 and 5", or as many grids as there are modulator systems, are modulated by diiferent messagesor signals. Of course, it is also possible to provide instead only one anode segment, say, segment 2'` with anopening serving for an exit of the electrons;

hence, only one accelerator grid, one control grid.

and one anode are employed in' such case. In an arrangement as shown in Figure 2, the pushpull or phase-opposed signal modulated voltages are put on co-axial energy feeder lines yand fed to another point. Also in this case, as schematically shown, the outer sheath or shield is in radio frequency connection with the accelerator electrodes 4', I".

Instead of providing distinct openings in the outer electrodes of the oscillation system, it would, of course, also be feasible to utilize the slits or splits between the various segments. As known, what emerges through the latter is an electron current which is ultra-radio frequency modulated, and this is useful for the purposes of the invention. Moreover, it may be advantageous to mount the modulation system, particularly the magnetron system, in tangential direction to the cathode rather than in radial direction. Such an arrangement is illustrated in Fig. 3 where I is the cathode, 2' and 2 the anode segments, and l the ultra-short wave oscillation circuit. One of the anode segments indicated at 2" has a tangentially directed opening 3' through which the electronsl reach the outer space. shall be described more fully further below.`

In order that the wave generation process may be affected as little as feasible, the opening giving exit to the electrons should. of course, be made as small as feasible. As a result,. naturally, also the electron current reaching the modulation system will be verv small, and this means low emciency or signal output. However, basically speaking, this drawback is quite immaterial inasmuch as only a small power is delivered from the frequency-governing system properly so-called for which it is merely the question of frequency stability that playsd'an essential part (as is true, tor instance, also of crystal-stabilized radio frequency transmitters v of standard design). Howevenacccrding to another object of `he invention, it is also possible to amplify this small current put out by the generator system inside the tube so that before or after the modulation process a substantial increase in power is securable.

An organizaticn of thi-s kind is illustrated in Figure 3 in which the electrons leaving the oscillation system l. 2' traverse first hollow cylindrical electrode 4"'. This electrode, if desired, may produce an electron-optic focusing effect together with its action as a space-charge grid. The electrons then enter a system operating ac- The rest of the arrangement of Fig. 3

cording tothe principle of secondary electron (emission) multiplication comprising the electrodes I, l'. What particular kind of secondary electron multiplication is used is immaterial. From the multiplier, the electron pencil reaches the modulation system. The latter comprises the control grid l and the anode 6. Instead of providing the electron-multiplying means between the oscillatory system and the modulation system, such multiplying could also be interposed between the modulator system and the useful or signal circuit. Also, both schemes could be practiced simultaneously.

The invention is not restricted to the exemplified embodiments here shown. Indeed, it may be applied to ultra-high-frequency oscillator tube system no matter of what kind or construction. Moreover, it could utilize any desired accessory electron-optic electron systems. The invention is further not restricted to modulation work, in fact, it could with equal success be used for regulator purposes, etc. The chief advantage inherent in the invention is its freedom from reaction between signal or output circuit and the generator. Indeed,the mere separation of the useful (signal) circuit and the generator circuit by means of electron coupling, even without modulation. would basically form the object of the invention.

What is claimed is:

l. In an ultra-high frequency signalling systern, an evacuated' container enclosing an electron emission element, `a plurality of oscillation generating electrodes comprising spaced surfaces points on which are at substantially equal distances from said emission element, a space between said surfaces permitting electrons emitted by said element to travel beyond said surfaces and additional electrodes including an anode and a control electrode located in the path of the electrons which pass through said lastmentioned space, means connecting a pair of said oscillation generating electrodes in an oscillation generating circuit in which circuit the frequency of the oscillations generated is controlled primarily by the electron transit timey between said oscillation generating electrodes, an output circuit connected with said anode electrode, said output rcircuit being coupled to said oscillation generating circuit substantially only by the electrons which pass beyond the generating electrodes and through said last named space, and means for modulating the potential on said control electrode to thereby modulate the electrons supplied to said output circuit from said electrodes in said oscillation generating circuit.

2. A system as recited in claim l wherein a ring-like electrode is located in said container vbetween said oscillation generating electrodes and said output electrode included in said output circuit.

3. In an ultra-high frequency signalling system, an evacuatedcontainer enclosing an electron emission element, a plurality of electrodes having surfaces points on which are substantially equally spaced from said emission element, said plurality of electrodes partially enclosing said emission element, and a plurality of corresponding electrodes on opposite sides of said emission element spaced different distances from said emission element, means connecting a pair of `said electrodes partially surrounding said emission element :n an oscillation generating circuit in which circuit the frequency of the oscillations generated is controlled primarily by the disposed between said generating electrodes and electrode on each side of said emission element l0 said electrodes connected by said output circuit. 4. A signalling system as recited in claim 3 wherein said container includes a ring-like electrode disposed between said generating electrodes and each of said electrodes connected by said output circuit.

HANS JACOB RITTER voN-BAEYER. HANS OTTO ROOSENSTEIN. HERBERT MUTH. 

